Power battery charging method, motor control circuit, and vehicle

ABSTRACT

The present disclosure provides a power battery charging method, a motor control circuit, and a vehicle. The motor control circuit includes a first switch module, a three-phase inverter, and a control module, where a power supply module, the first switch module, the three-phase inverter, and a three-phase alternating current motor form a current loop, the three-phase alternating current motor inputs or outputs a current by using a wire N extending from a connection point of three phase coils, and the control module controls the three-phase inverter, so that the motor control circuit receives a voltage of the power supply module and outputs a direct current. In the technical solutions, a wire N extends from the three-phase alternating current motor, and further forms different charging loops with the three-phase inverter, the three-phase alternating current motor, and the power battery. When it is detected that the voltage of the power supply module is not higher than a voltage of the power battery, the original three-phase inverter and three-phase alternating current motor are adopted to boost the voltage of the power supply module before the power battery is charged, and in this way, no extra external boost circuit needs to be added, which reduces costs of the additional circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based upon and claims priority to ChinesePatent Application No. 201811574168.8, filed on Dec. 21, 2018, which isincorporated herein by reference in its entirety.

FIELD

The present disclosure relates to the technical field of motor controland, in particular, to a power battery charging method, a motor controlcircuit, and a vehicle.

BACKGROUND

With development and rapid popularization of electric vehicles, chargingtechnologies of power batteries of the electric vehicles have becomeincreasingly important. The charging technologies need to meet needs ofdifferent users, and adaptability and compatibility of the powerbatteries of the electric vehicles and charging piles.

Currently, manners of direct current charging of the power batteries aregenerally classified into two manners: a manner of direct charging and amanner of boost charging. The direct charging means that positive andnegative electrodes of a charging pile are directly connected topositive and negative bus bars of the power battery through a contactoror a relay to directly charge the battery, without an intermediate boostor buck circuit; and boost charging means that a DC/DC bridge circuitcapable of bidirectional buck-boost is added and connected to thepositive and negative bus bars between the charging pile and the powerbattery in parallel.

For the direct charging, when the maximum output voltage of the chargingpile is lower than a voltage of the power battery, the charging pilecannot charge the battery; and for the boost charging, a boost circuitincluding a DC/DC bridge circuit, an inductor, and a correspondingcontrol detection circuit further separately need to be added, whichincreases a volume and costs of an entire apparatus.

SUMMARY

A purpose of the present disclosure is to provide a power batterycharging method, a motor control circuit, and a vehicle, to resolve aproblem in the related art that a volume and costs of an entireapparatus are increased because a boost circuit needs to be added when apower battery is charged in a manner of boost charging.

The present disclosure is implemented as follows: According to a firstaspect of the present disclosure, a motor control circuit is provided,including a first switch module, a three-phase inverter, and a controlmodule, where a power supply module, the first switch module, thethree-phase inverter, and a three-phase alternating current motor form acurrent loop, midpoints of three phase legs of the three-phase inverterare respectively connected to three phase coils of the three-phasealternating current motor, the three-phase alternating current motorinputs or outputs a current by using a wire N extending from aconnection point of the three phase coils, the control module isseparately connected to the three-phase inverter, the first switchmodule, the three-phase alternating current motor, and the power supplymodule, and the control module controls the three-phase inverter, sothat the motor control circuit receives a voltage of the power supplymodule and outputs a direct current.

According to a second aspect of the present disclosure, a power batterycharging method is provided, based on the motor control circuitaccording to the first aspect, where the charging method includes:

obtaining a voltage of the power supply module and a voltage of a powerbattery, and selecting a charging manner based on the voltage of thepower supply module and the voltage of the power battery, where thecharging manner includes boost charging manner and direct chargingmanner; and

controlling the first switch module and the second switch module toclose so that the power supply module outputs a direct current, andcontrolling the three-phase inverter so that the power supply modulecharges the power battery in the selected charging manner.

According to a third aspect of the present disclosure, a vehicle isprovided, where the vehicle includes the motor control circuit accordingto the first aspect.

The present disclosure provides a power battery charging method, a motorcontrol circuit, and a vehicle. The motor control circuit includes afirst switch module, a three-phase inverter, and a control module, wherea power supply module, the first switch module, the three-phaseinverter, and a three-phase alternating current motor form a currentloop, midpoints of three phase legs of the three-phase inverter arerespectively connected to three phase coils of the three-phasealternating current motor, the three-phase alternating current motorinputs or outputs a current by using a wire N extending from aconnection point of the three phase coils, the control module isseparately connected to the three-phase inverter, the first switchmodule, the three-phase alternating current motor, and the power supplymodule, and the control module controls the three-phase inverter, sothat the motor control circuit receives a voltage of the power supplymodule and outputs a direct current. In the technical solutions of thepresent disclosure, the wire N extends from the three-phase alternatingcurrent motor, and forms different charging loops with the three-phaseinverter, the three-phase alternating current motor, and the powerbattery. When the control module detects that a highest output voltageof the power supply module is not higher than the voltage of the powerbattery, the original three-phase inverter and three-phase alternatingcurrent motor are adopted to boost the voltage of the power supplymodule before the power battery is charged; or when the control moduledetects that a highest output voltage of the power supply module ishigher than the voltage of the power battery, the power battery ischarged directly. In this case, the power battery can be chargedregardless of the voltage of the power supply module, and therebyachieving robust compatibility and adaptability. In addition, no extraexternal boost circuit needs to be added, which reduces costs of anexternal circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solutions of the embodiments of the presentdisclosure more clearly, the following briefly introduces theaccompanying drawings for describing the embodiments. Apparently, theaccompanying drawings in the following description show only someembodiments of the present disclosure, and a person of ordinary skill inthe art may still derive other drawings from these accompanying drawingswithout creative efforts.

FIG. 1 is a schematic structural diagram of a motor control circuitaccording to one embodiment of the present disclosure;

FIG. 2 is another schematic structural diagram of a motor controlcircuit according to one embodiment of the present disclosure;

FIG. 3 is a circuit diagram of a motor control circuit according to oneembodiment of the present disclosure;

FIG. 4 is another circuit diagram of a motor control circuit accordingto one embodiment of the present disclosure;

FIG. 5 is a flowchart of a power battery charging method according toanother embodiment of the present disclosure;

FIG. 6 is a current path diagram of a motor control circuit using apower battery charging method according to another embodiment of thepresent disclosure;

FIG. 7 is another current path diagram of a motor control circuit usinga power battery charging method according to another embodiment of thepresent disclosure; and

FIG. 8 is still another current path diagram of a motor control circuitusing a power battery charging method according to another embodiment ofthe present disclosure.

DETAILED DESCRIPTION

To make the objectives, technical solutions, and advantages of thepresent disclosure clearer and more comprehensible, the followingfurther describes the present disclosure in detail with reference to theaccompanying drawings and embodiments. It is to be understood that thedisclosed embodiments described herein are merely used for describingthe present disclosure, but are not intended to limit the presentdisclosure.

To describe the technical solutions in the present disclosure, thefollowing will be described by using various embodiments.

One embodiment of the present disclosure provides a motor controlcircuit. As shown in FIG. 1, the motor control circuit includes a firstswitch module 102, a three-phase inverter 104, and a control module 108,where a power supply module 101, the first switch module 102, thethree-phase inverter 104, and a three-phase alternating current motor103 forms a current loop, midpoints of three phase legs of thethree-phase inverter 104 are respectively connected to three phase coilsof the three-phase alternating current motor 103, the three-phasealternating current motor 103 inputs or outputs a current by using awire N extending from a connection point of the three phase coils, thecontrol module 108 is separately connected to the three-phase inverter104, the first switch module 102, the three-phase alternating currentmotor 103, and the power supply module 101, and the control module 108controls the three-phase inverter 104, so that the motor control circuitreceives a voltage of the power supply module 101 and outputs a directcurrent.

Power provided by the power supply module 101 may be in power forms suchas a direct current provided by a direct current charging pile, a directcurrent outputted after rectification of a single-phase or three-phasealternating current charging pile, electric energy generated by a fuelbattery, or a direct current obtained after a controller of a generatorrectifies electricity generated by the generator driven when a rangeextender such as the motor rotates. The first switch module 102 isconfigured to connect the power supply module 101 to a circuit based ona control signal, so that the power supply module 101, the first switchmodule 102, the three-phase alternating current motor 103, and thethree-phase inverter form a current loop. The first switch module 102may be a switch disposed at a positive electrode and/or a negativeelectrode of the power supply module 101 to implement on-off control ofan output current of the power supply module 101. The three-phasealternating current motor 103 includes three phase coils, and the threephase coils are connected to a midpoint. The three-phase alternatingcurrent motor 103 may be a permanent-magnet synchronous motor orasynchronous motor, and the three-phase alternating current motor 103 isa three-phase four-wire system, that is, a wire N extending from aconnection point of the three phase coils is configured to input oroutput a current. The three-phase inverter 104 includes six power switchunits, and the power switch may be a device type such as a transistor,an IGBT, and a MOS transistor. Two power switch units form one phaseleg, a total of three phase legs are formed, and a connection point oftwo power switch units in each phase leg is connected to one phase coilin the three-phase alternating current motor 103. The control module 108may collect a voltage, a current, and temperature of the power battery106, a phase current of the three-phase alternating current motor 103,and a voltage of the power supply module 101. The control module 108 mayinclude a controller of an entire vehicle, a control circuit of a motorcontroller, and a circuit of a BMS battery manager that are connectedthrough a CAN wire. Different modules in the control module 108 controlon-off of the power switches in the three-phase inverter 104 and on-offof the first switch module 102 based on obtained information toimplement closing of different current loops.

When the first switch module 102 is controlled to connect the powersupply module 101 to the circuit, for example, when a direct currentcharging terminal is plugged into a direct current charging interface ofthe vehicle, the control module 108 compares the voltage of the powersupply module 101 with a voltage of a to-be-charged component. Forexample, the to-be-charged component may be a rechargeable battery, anda different charging manner is selected to charge the power batterybased on a comparison result. When the voltage of the power supplymodule 101 is not higher than the voltage of the power battery, thepower battery may be charged in a direct current boost charging manner.Because the three phase coils of the three-phase alternating currentmotor 103 may store electric energy, the first switch module 102 and asecond switch module 105 may be controlled to close, and the three-phaseinverter 104 may be used, so that the power supply module 101, thethree-phase inverter 104, and the three phase coils of the three-phasealternating current motor 103 form an inductive energy storage loop.Even if the power supply module 101 first charges the three phase coilsof the three-phase alternating current motor 103, and the power battery106 is then charged by using the power supply module 101 and the threephase coils of the three-phase alternating current motor 103, becausethe three phase coils of the three-phase alternating current motor 103also output a voltage at this time, the voltage outputted by the powersupply module 101 is superimposed with the voltage outputted by thethree phase coils, so that the voltage of the power supply module 101 isboosted, thereby normally charging the power battery. When the controlmodule 108 detects that the voltage of the power supply module 101 ishigher than the voltage of the power battery, the control module 108controls the first switch module 102 to close, so that an external powersupply charges the power battery by using the three-phase alternatingcurrent motor 103 and the three-phase inverter 104.

In the embodiments of the present disclosure, the wire N extends fromthe three-phase alternating current motor, and forms different chargingloops with the three-phase inverter, the three-phase alternating currentmotor, and the power battery. When the control module detects that ahighest output voltage of the power supply module is not higher than thevoltage of the power battery, the original three-phase inverter andthree-phase alternating current motor are adopted to boost the voltageof the power supply module before the power battery is charged; or whenthe control module detects that a highest output voltage of the powersupply module is higher than the voltage of the power battery, the powerbattery is charged directly. In this case, the power battery can becharged regardless of the voltage of the power supply module, andthereby achieving robust compatibility and adaptability. In addition, noextra external boost circuit needs to be added, which reduces costs ofan external circuit.

As shown in FIG. 2, in an embodiment of the present disclosure, themotor control circuit further includes a second switch module 105, thethree-phase inverter 104 is connected to a power battery 106 by thesecond switch module 105, and the second switch module 105 is connectedto the control module 108.

The second switch module 105 is configured to connect or disconnect thepower battery 106 to or from a circuit.

In a first implementation of the second switch module 105, the secondswitch module 105 is a third switch, and the third switch is connectedbetween a first terminal of the three-phase inverter 104 and a positiveelectrode of the power battery 106.

In a second implementation of the second switch module 105, the secondswitch module 105 is a fourth switch, and the fourth switch is connectedbetween a second terminal of the three-phase inverter 104 and a negativeelectrode of the power battery.

In a third implementation of the second switch module 105, the secondswitch module 105 includes the third switch and the fourth switch.

In a first implementation of the first switch module, the first switchmodule 102 is a first switch, and the first switch is connected betweena positive electrode of the power supply module 101 and the connectionpoint of the three phase coils of the three-phase alternating currentmotor 103.

In a second implementation of the first switch module 102, the firstswitch module 102 is a second switch, and the second switch is connectedbetween a negative electrode of the power supply module 101 and thesecond terminal of the three-phase inverter 104.

In a third implementation of the first switch module 102, the firstswitch module 102 includes the first switch and the second switch.

A connection relationship in this implementation may be as follows: Afirst terminal and a second terminal of the first switch module 102 areconnected to the positive electrode and the negative electrode of thepower supply module 101, a third terminal of the first switch module 102is connected to the connection point of the three phase coils in thethree-phase alternating current motor 103, a fourth terminal of thefirst switch module 102 is connected to the second terminal of thethree-phase inverter 104 and a second terminal of the second switchmodule 105, the first terminal of the three-phase inverter 104 isconnected to a first terminal of the second switch module 105, and athird terminal and a fourth terminal of the second switch module 105 areconnected to the positive electrode and the negative electrode of thepower battery 106.

The first switch module 102 includes a first switch and a second switch,and the second switch module 105 includes a third switch and a fourthswitch. A first terminal and a second terminal of the first switch arerespectively the first terminal and the third terminal of the firstswitch module 102, and a first terminal and a second terminal of thesecond switch are respectively the second terminal and the fourthterminal of the first switch module 102, a first terminal and a secondterminal of the third switch are respectively the first terminal and thethird terminal of the second switch module 105, and a first terminal anda second terminal of the fourth switch are respectively the secondterminal and the fourth terminal of the second switch module 105.

For the three-phase inverter 104, specifically, the three-phase inverter104 includes a first power switch unit, a second power switch unit, athird power switch unit, a fourth power switch unit, a fifth powerswitch unit, and a sixth power switch unit, and control terminal of eachpower switch unit is connected to the control module 108. Inputterminals of the first power switch unit, the third power switch unit,and the fifth power switch unit are jointly connected to form the firstterminal of the three-phase inverter 104, and output terminals of thesecond power switch unit, the fourth power switch unit, and the sixthpower switch unit are jointly connected to form the second terminal ofthe three-phase inverter 104. A first coil of the three-phasealternating current motor 103 is connected to the output terminal of thefirst power switch unit and the input terminal of the fourth powerswitch unit. A second coil of the three-phase alternating current motor103 is connected to the output terminal of the third power switch unitand the input terminal of the sixth power switch unit. A third coil ofthe three-phase alternating current motor 103 is connected to the outputterminal of the fifth power switch unit and the input terminal of thesecond power switch unit.

The first power switch unit and the fourth power switch unit in thethree-phase inverter 104 form an A-phase leg, the third power switchunit and the sixth power switch unit form a B-phase leg, and the inputterminal of the fifth power switch unit and the second power switch unitform a C-phase leg. A control manner of the three-phase inverter 104 maybe a combination of any one or more of the following: for example, atotal of 7 heating control methods for any phase leg, or any two phaselegs, and three phase legs of the three phases A, B, and C, which isflexible and simple. The switching of the phase legs can help selecthigh, medium or low heating power. For example, for low-power heating, apower switch of any phase leg may be selected for control, and the threephase legs may be switched in turn. For example, the A-phase leg firstindependently operates, to control the first power switch unit and thefourth power switch unit to perform heating for a period of time; thenthe B-phase leg independently operates, to control the third powerswitch unit and the sixth power switch unit to perform heating for thesame period of time; and then the C-phase leg independently operates, tocontrol the fifth power switch unit and the second power switch unit toperform heating for the same period of time, and then the C-phase leg isswitched to the A-phase leg for operating cyclically, so that thethree-phase inverter 104 and the three phase coils are electrified andheated in turn, to make the three-phase heating more balanced. Forexample, for medium power heating, power switches of any two phase legsmay be selected for control, and the three phase legs can be switched inturn. For example, the A-phase and B-phase legs operate first to controlthe first power switch unit, the fourth power switch unit, the thirdpower switch unit, and the sixth power switch unit to perform heatingfor a period of time; then the B-phase and C-phase legs operate tocontrol the third power switch unit, the sixth power switch unit, thefifth power switch unit, and the second power switch unit to performheating for the same period of time; and then the C-phase and A-phaselegs operate to control the fifth power switch unit, the second powerswitch unit, the first power switch unit, and the fourth power switchunit to perform heating for the same period of time, and then theC-phase and A-phase legs are switched to the A-phase and B-phase legsfor operating cyclically, to make heating of the three-phase inverter104 and three phase coils more balanced. For example, for high-powerheating, power switches of the three phase legs may be selected forcontrol, and because a three-phase loop is theoretically balanced, thethree-phase current is balanced, and as a result, heating of thethree-phase inverter 104 and the three phase coils is balanced and thethree-phase currents are basically the direct current, and averagevalues are basically the same; and because three-phase winding groupsare symmetrical, three-phase synthetic magnetomotive force inside themotor is basically zero in this case, and therefore, the stator magneticfield is basically zero, and basically, no torque is generated for themotor, which helps greatly reduce stress of a drive system.

The technical solutions of the present disclosure are described indetail below by using a specific circuit structure:

FIG. 3 is a schematic circuit diagram of a motor control circuitaccording to the present disclosure. For ease of description of themotor control circuit, in the foregoing figure, other electrical devicesare omitted, and only the power battery 106, the three-phase inverter104, and the three-phase alternating current motor 103 are taken intoconsideration. The first switch module 102 includes a switch K1 and aswitch K2. The second switch module 105 includes a switch K3 and aswitch K4. In the three-phase inverter 104, the first power switch unitincludes a first upper phase leg VT1 and a first upper bridge diode VD1,the second power switch unit includes a second lower phase leg VT2 and asecond lower bridge diode VD2, the third power switch unit includes athird upper phase leg VT3 and a third upper bridge diode VD3, the fourthpower switch unit includes a fourth lower phase leg VT4 and a fourthlower bridge diode VD4, the fifth power switch unit includes a fifthupper phase leg VT5 and a fifth upper bridge diode VD5, and the sixthpower switch unit includes a sixth lower phase leg VT6 and a sixth lowerbridge diode VD6. The three-phase alternating current motor 103 is athree-phase four-wire system, and a wire N extends from the connectionpoint of the three phase coils, and the wire N is connected to theswitch K1. The three phase coils are separately connected to the upperand lower phase legs of the phases A, B, and C in the three-phaseinverter 104, and both terminals of the power battery 106 are alsoconnected to a capacitor C2 in parallel.

FIG. 4 is another schematic circuit diagram of a motor control circuitaccording to the present disclosure. A difference from FIG. 3 is asfollows: An inductor L1 is connected in series between the switch K1 andthe positive electrode of the power supply module 101, and a capacitorC1 is connected in parallel among the power supply module, the switchK1, and the switch K2. The capacitor C1 may be selected based on relatedlocal charging regulations, charging protocols, and the like, and acapacitance value can be adjusted based on an actual need. It should benoted that the inductor L1 may be further disposed between the capacitorC1 and the switch K1.

Another embodiment of the present disclosure provides a power batterycharging method, based on the motor control circuit shown in FIG. 5, thecharging method includes the following steps.

S101: Obtain a voltage of the power supply module and a voltage of thepower battery, and select a charging manner based on the voltage of thepower supply module and the voltage of the power battery, where thecharging manner includes boost charging manner and direct charging.

S102: Control the first switch module to close so that the power supplymodule outputs a direct current, and control the three-phase inverter sothat the power supply module charges the power battery in the selectedcharging manner.

In the foregoing steps, as shown in FIG. 1, an execution body is thecontrol module 108, and when the control module 108 detects that thepower supply module 101 is connected to the circuit, for example, when acharging terminal is plugged into a direct current charging interface ofa vehicle, the control module 108 compares a voltage of the power supplymodule 101 with a voltage of the power battery 106. A different chargingmanner is selected to charge the power battery 106 based on a comparisonresult. When a highest output voltage of the power supply module 101 isnot higher than the voltage of the power battery 106, the power battery106 may be charged in a direct current boost charging manner. Becausethe three phase coils of the three-phase alternating current motor 103may store electric energy, the first switch module 102 may be controlledto close, and the three-phase inverter 104 may be controlled, so thatthe power supply module 101 charges the three phase coils of thethree-phase alternating current motor 103, and the power battery 106 isthen charged through the power supply module 101 and the three phasecoils of the three-phase alternating current motor 103. Because thethree phase coils of the three-phase alternating current motor 103 alsooutput a voltage at this time in a discharge process, the voltageoutputted by the power supply module 101 is superimposed with thevoltage outputted by the three phase coils, so that the voltage of thepower supply module 101 is boosted, thereby normally charging the powerbattery 106. When the control module 108 detects that a highest outputvoltage of the power supply module 101 is higher than the voltage of thepower battery 106, the control module 108 controls the first switchmodule 102 to close, so that an output voltage of the power supplymodule 101 is used to directly charge the power battery 106. In theembodiments of the present disclosure, the wire N extends from the threephase coils in the three-phase alternating current motor, and formsdifferent charging and discharging loops with the power battery and thethree-phase inverter. When the control module detects that a highestoutput voltage of the power supply module is not higher than the voltageof the power battery, the original three-phase inverter 104 andthree-phase alternating current motor are adopted to boost the voltageof the power supply module before the power battery is charged; or whenthe control module detects that a highest output voltage of the powersupply module is higher than the voltage of the power battery, thevoltage of the power supply module is configured to directly charge thepower battery. In this case, the power battery can be charged regardlessof the voltage of the power supply module, and thereby achieving robustcompatibility and adaptability. In addition, no extra external boostcircuit needs to be added, which reduces costs of an external circuit.

Further, the selecting a charging manner based on the voltage of thepower supply module and the voltage of the power battery includes:selecting the boost charging manner when it is detected that the voltageof the power supply module is not higher than the voltage of the powerbattery.

The controlling the three-phase inverter so that the power supply modulecharges the power battery in the selected charging manner includes:controlling the three-phase inverter so that a process of charging threephase coils of the three-phase alternating current motor by the powersupply module and a process of discharging the power battery by thepower supply module and the three phase coils of the three-phasealternating current motor are alternately performed, to boost a chargingvoltage of the power supply module before the power battery is charged.

In an implementation, as shown in FIG. 1, the power supply module 101,the first switch module 102, the three-phase alternating current motor103, and the three-phase inverter 104 form a charging loop, and thepower supply module 101, the first switch module 102, and thethree-phase alternating current motor 103, the three-phase inverter 104,and the power battery 106 form a discharging loop.

The controlling the three-phase inverter so that a process of chargingthree phase coils of the three-phase alternating current motor by thepower supply module and a process of discharging the power battery bythe power supply module and the three phase coils of the three-phasealternating current motor are alternately performed includes:controlling the three-phase inverter 104 to perform alternate closing onthe charging loop and the discharging loop.

In this implementation, a neutral wire extends from the three-phasealternating current motor 103, and is connected to the power supplymodule 101 through the first switch module 102, and may further form thecharging loop and the discharging loop in the three-phase alternatingcurrent motor 103 with the power supply module 101, the three-phaseinverter 104, and the power battery 106 by controlling the three-phaseinverter 104. By controlling the alternate closing of the charging loopand the discharging loop, the power battery 106 may also be charged evenif the voltage of the power supply module 101 is not higher than thevoltage of the power battery 106, thereby achieving robust compatibilityand adaptability. In addition, no extra external boost circuit needs tobe added, which reduces costs of an external circuit.

For the three-phase inverter 104, in an implementation, the three-phaseinverter 104 includes three phase legs, each phase leg includes twopower switch units connected in series, and the three phase coils of thethree-phase alternating current motor 103 are separately connected toconnection points of two power switch units of each phase leg.

The controlling the three-phase inverter so that a process of chargingthe three phase coils of the three-phase alternating current motor bythe power supply module and a process of discharging the power batteryby the power supply module and the three phase coils of the three-phasealternating current motor are alternately performed includes:

controlling two power switch units on at least one phase leg of thethree-phase inverter 104 to close alternately so that the process ofcharging the three phase coils of the three-phase alternating currentmotor 103 by the power supply module 101 and the process of dischargingthe power battery 106 by the power supply module 101 and the three phasecoils of the three-phase alternating current motor 103 are alternatelyperformed.

For the control of the three-phase inverter 104, switching of differentphase legs can be controlled for connection as needed to implement thedirect current charging function. For example, the phase leg thatcontrols the connection may be any phase leg, any two phase legs, andthe three phase legs in the three phase legs, thereby implementing atotal of 7 switching charging manners.

Further, the controlling two power switch units to close alternately onat least one phase leg of the three-phase inverter includes: obtaining aquantity of to-be-connected phase legs of the three-phase inverter 104based on to-be-charged power of the power battery 106, and based on thequantity of to-be-connected phase legs, controlling a correspondingquantity of phase legs to operate.

A quantity of to-be-connected phase legs may be selected based onmagnitude of the to-be-charged power of the power battery 106. Theto-be-charged power of the power battery 106 may be obtained accordingto a charging power instruction sent by a battery manager. To controlthe corresponding quantity of phase legs to operate means to enable acurrent to flow on the phase legs. That is, the two power switch unitsin the phase legs close alternately to participate in different currentloops. For example, for low-power boost charging, any phase leg may beselected to operate for boost charging. For medium-power boost charging,any two phase legs may be selected to operate for boost charging, andfor high-power boost charging, three phase legs may be selected tooperate simultaneously for boost charging.

In this implementation, based on the to-be-charged power of the powerbattery, a corresponding quantity of phase legs are selected to operatefor boost charging, and a corresponding control manner is implementedbased on the to-be-charged power of the power battery, which improvesthe charging efficiency of the power battery.

In the first implementation, the obtaining a quantity of to-be-connectedphase legs of the three-phase inverter based on to-be-charged power ofthe power battery, and based on the quantity of to-be-connected phaselegs, controlling a corresponding quantity of phase legs to operateincludes:

determining that the quantity of to-be-connected phase legs of thethree-phase inverter 104 is 1 when it is detected that the to-be-chargedpower of the power battery 106 is lower than first preset power, andcontrolling any phase leg in the three phase legs to operate orcontrolling the three phase legs to operate alternately.

When the control module 108 detects that the to-be-charged power of thepower battery 106 is relatively low, a charging need may be met bycontrolling one of the three phase legs to close. It is assumed that thethree phase legs include an A-phase leg, a B-phase leg, and a C-phaseleg, and any phase leg in the three phase legs may be controlled tocontinuously operate, or the three phase legs may be controlled to beswitched for operation in turn. To switch the three phase legs foroperation in turn means that the three phase legs are to operate insequence. For example, the A-phase leg is first controlled to operate,and the B-phase leg and the C-phase leg do not operate; then the B-phaseleg is controlled to operate, and the A-phase leg and the C-phase leg donot operate; then the C-phase leg is controlled to operate, and theA-phase leg and the B-phase leg do not operate; and then the three phaselegs are controlled to be switched in turn, so that heating of thethree-phase inverter 104 and the three phase coils is balanced.

In a second implementation, the obtaining a quantity of to-be-connectedphase legs of the three-phase inverter based on to-be-charged power of apower battery, and based on the quantity of to-be-connected phase legs,controlling a corresponding quantity of phase legs to operate includes:determining that the quantity of to-be-connected phase legs of thethree-phase inverter 104 is 2 when it is detected that the to-be-chargedpower of the power battery 106 is not lower than the first preset powerbut lower than second preset power, and controlling any two phase legsin the three phase legs to operate or controlling three groups of twophase legs in the three phase legs to operate in sequence, where thethree-phase inverter includes an A-phase leg, a B-phase leg, and aC-phase leg, a first group of two phase legs include the A-phase leg andthe B-phase leg, a second group of two phase legs include the A-phaseleg and the C-phase leg, and a first group of three phase legs includethe B-phase leg and the C-phase leg.

When the control module 108 detects that the to-be-charged power of thepower battery 106 is not lower than the first preset power and lowerthan the second preset power, two of the three phase legs close to meetthe charging need, and any two phase legs in the three phase legs may becontrolled to continuously operate, and three groups of two phase legsin the three phase legs may also be controlled to be switched foroperation in turn. For example, the A-phase leg and the B-phase leg maybe considered as the first group of two phase legs, the A-phase leg andthe C-phase leg may be considered as the second group of two phase legs,and the B-phase leg and the C-phase leg may be considered as the thirdgroup of two phase legs. That is, the first group of two phase legs arefirst controlled to operate, and the C-phase leg does not operate; thenthe second group of two phase legs are controlled to operate, and theB-phase leg does not operate; then the third group of two phase legs arecontrolled to operate, and the A-phase leg does not operate; and thenthe three groups of two phase legs are controlled to be switched foroperation in turn, so that heating of the three-phase inverter 104 andthe three phase coils is balanced.

In a second implementation, further, after the determining that thequantity of to-be-connected phase legs of the three-phase inverter is 2when the control module detects that the to-be-charged power of thepower battery is not lower than the first preset power but lower thansecond preset power, the method further includes: there is a 180-degreedifference between phases of PWM control signals sent by the controlmodule 108 separately to the two phase legs.

To reduce overall ripples of a charging circuit, a manner of controllingthe switch of the inverter at staggered phases is used, and when onlytwo phase legs are used, a difference between phases of two-phasecontrol signals separately sent to the two phase legs is about 180degrees. In this case, positive and negative ripples of the two phasecoils are superimposed on each other and cancel each other, so that theoverall ripples can be greatly reduced.

In a third implementation, the obtaining, by the control module, aquantity of to-be-connected phase legs of the three-phase inverter basedon to-be-charged power of the power battery, and based on the quantityof to-be-connected phase legs, controlling a corresponding quantity ofphase legs to operate includes: determining that the quantity ofto-be-connected phase legs of the three-phase inverter 104 is 3 when thecontrol module 108 detects that the to-be-charged power of the powerbattery 106 is not lower than the second preset power, and controllingthe three phase legs to operate simultaneously.

When the control module 108 detects that the to-be-charged power of thepower battery 106 is relatively high, three of the three phase legsclose to meet the charging need, and the three phase legs in the threephase legs are controlled to operate simultaneously. Because thethree-phase loop is theoretically balanced, the current outputted by thethree phase legs is balanced, and heating of the three-phase inverter104 and the three phase coils is balanced.

In the third implementation, further, after the determining that thequantity of to-be-connected phase legs of the three-phase inverter is 3when the control module detects that the to-be-charged power of thepower battery is not lower than second preset power, the method furtherincludes: sending PWM control signals at the same phase to the threephase legs; or sending PWM control signals at different phases to thethree phase legs, where differences between a phase of a PWM controlsignal of one phase leg and phases of PWM control signals of the othertwo phase legs are 120 degrees and −120 degrees respectively.

To reduce the overall ripples of the charging circuit, a manner ofcontrolling the switch of the inverter at staggered phases is used, andwhen all the three phase legs are controlled to operate, a differencebetween phases of three-phase control signals outputted to the threephase legs is about 120 degrees. In this case, positive and negativeripples of the three phase coils are superimposed on each other andcancel each other, so that the overall ripples may be greatly reduced. Asynchronous control manner may also be used, that is, power switches ofthe three phase legs are simultaneously controlled, synchronously turnedon, and synchronously turned off. In this case, three-phase currentssimultaneously increase when the power switches are turned on, andsimultaneously decrease when the power switches are turned off. As aresult, the three-phase currents tend to be equal at any moment, thethree-phase synthetic magnetomotive force tends to be zero, the statormagnetic field tends to be zero, and basically, no torque is generatedfor the motor.

In the third implementation, further, the control module 108 obtains acurrent value of each phase leg when the three phase legs operatesimultaneously, and adjusts a control signal for each phase leg so thataverage current values of the three phase legs are within the samepreset current range.

Occasionally, in an actual circuit, because the three-phase alternatingcurrent motor 103 may not necessarily have the same three-phase loop asthe motor controller, the three-phase currents are not necessarily equalduring open-loop control, and a long-term current difference may becomeincreasingly large, and therefore, independent closed-loop control isrequired for the three-phase currents, and the average values of thethree-phase currents are controlled to be within the same preset balancevalue accuracy range.

In the third implementation, further, the control module 108 obtains acurrent value of each phase leg when the three phase legs operatesimultaneously, and adjusts a control signal for each phase leg so thatthe current values of the three phase legs are not exactly the same anda current difference between each two phase legs is less than a presetcurrent threshold.

When independent closed-loop control is performed on the three-phasecurrents, a one-phase current is controlled to be slightly higher thanthe other two-phase currents, and the other two-phase currents may becontrolled to be two-phase currents with an equal average value orslightly unequal currents, so that a magnetic field generated by thethree-phase currents may not be zero but very small, and in this case,motor torque is not zero but very small. In this way, a motor shaft mayoutput small torque on the vehicle, to mesh gears, and reduce jitteringand noise caused by torque fluctuation. A value of the current andmagnitude of the outputted torque may be determined by controllingvalues of the three-phase currents based on a need in the actual case.

In an implementation, the following manner can be used to control thealternate closing of the charging loop and the discharging loop: Thecontrol module 108 outputs a PWM control signal to the three-phaseinverter 104 to perform alternate closing on the charging loop and thedischarging loop, obtains the to-be-charged power of the power battery106, obtains a corresponding current based on the to-be-charged power,compares an actual charging current of the power battery 106 with thecorresponding current obtained based on the to-be-charged power, andadjusts a duty cycle of the PWM control signal based on a comparisonresult, to adjust a current outputted to the power battery 106.

The control module 108 receives the to-be-charged power sent by thebattery manager, and then obtains a corresponding current based on theto-be-charged power, and compares the charging current for charging thepower battery 106 with the corresponding current obtained based on theto-be-charged power. When the charging current is less than a currentvalue corresponding to the required charging power, an on duty cycle ofPWM is adjusted and added; or when the charging current is greater thanthe current value corresponding to the required charging power, the onduty cycle of the PWM is adjusted and reduced until the charging poweris met.

The technical solution of the present disclosure is described in detailbelow by using a specific circuit structure shown in FIG. 3.

The control steps of the control module 108 specifically include:

Step 1: The control module 108 controls the switches K1, K2, K3, and K4to close.

Step 2: As shown in FIG. 6, the control module 108 sends a PWM controlsignal to the three-phase inverter 104, and during a connection timeperiod in each PWM control signal cycle, the control module 108 controlsconnection of a fourth lower phase leg VT4 of a phase A in thethree-phase inverter 104; a switch of a first upper phase leg VT1 isdisconnected, and upper and lower bridge power switches of the other twophases B and C are all disconnected. In this case, connection of theA-phase coil is implemented, a current is increased, an inductor startsto store energy. An A-phase inductive voltage is positive at the rightend and negative at the left end, while the inductive voltages of thephases B and C are opposite to that of the phase A.

Step 3: As shown in FIG. 7, during a disconnection time period in eachPWM control signal cycle, the control module 108 controls disconnectionof the fourth lower phase leg VT4 of the phase A in the three-phaseinverter 104; a switch of the first upper phase leg VT1 is connected,and upper and lower bridge power switches of the other two phases B andC are all disconnected. Freewheeling of the A-phase current isimplemented by using an upper bridge diode, an inductor starts todischarge, and a current is decreased. In this case, an A-phaseinductive voltage is positive at the left end and negative at the rightend, while the inductive voltages of the phases B and C are opposite tothat of the phase A. The A-phase inductive voltage is superimposed withthe voltage of the power supply module 101, to charge the battery at aboosted voltage.

Step 4: The control module 108 collects a charging current for thebattery, where when the current is less than a current valuecorresponding to required charging power, an on duty cycle of PWM isadjusted and added; or when the current is greater than the currentvalue corresponding to the required charging power, the on duty cycle ofthe PWM is adjusted and reduced until the charging power is met. Inaddition, three-phase current of the motor is detected to facilitateover-current and over-temperature control.

Step 5. Before the battery is fully charged, repeatedly perform step 2to step 4; or if the battery is fully charged, control the detectioncircuit to disconnect the switches K1, K2, K3, and K4.

For ease of understanding, current flow direction arrows in the energystorage period and the discharge period are marked both in FIG. 6 andFIG. 7. The two figures only show a switching method of using theA-phase leg and the A-phase coil for charging. Any one of the B-phase orC-phase leg and any one of the B-phase or C-phase coil may be switchedto based on a need, to implement charging, and a charging control mannerin which any two phase legs or three phase coils of the three phase legssimultaneously operate may be switched to.

It is assumed that a maximum output voltage of the direct currentcharging pile is higher than the voltage of the power battery 106, andin a specific implementation, FIG. 8 is a schematic circuit diagram ofan embodiment of a motor control circuit according to the presentdisclosure, and a connection method is exactly the same as that in FIG.3. During direct charging, the three phase coils are naturally connectedthrough the upper bridge diode of the three-phase inverter 104 to formthe three-phase charging current. Therefore, unlike boost charging, inthis charging manner, different three phase legs and coils cannot beswitched. In a specific implementation, to implement the direct chargingmanner, as shown in FIG. 8, the control steps specifically include:

Step 1: A control module 108 controls all six power switches of athree-phase inverter 104 to be disconnected.

Step 2: The control module 108 controls switches K1, K2, K3, and K4 toclose, and the power supply module 101 starts to supply power, andstarts to charge the power battery 106 by using the three phase coils ofthe three-phase alternating current motor 103 and the upper bridge diodeof the three-phase inverter 104, where a value of the charging currentis controlled by sending charging power or a charging current by thecontrol module 108 to the direct current charging pile.

Step 3: The control module 108 collects a battery charging current andthree-phase currents of a motor to control over-current andover-temperature in the charging process.

Step 4: Before the power battery is fully charged, repeatedly performsteps 2 and step 3; or if the power battery is fully charged, thecontrol module 108 disconnects the switches K1, K2, K3, and K4.

For ease of understanding, current flow direction arrows are marked inFIG. 8. The three-phase currents are direct currents, average valuesthereof are basically the same, and three-phase heating of the motor isbasically the same as that of the inverter. In addition, becausethree-phase winding groups are symmetrical, three-phase syntheticmagnetomotive force inside the motor is basically zero in this case, andtherefore, the stator magnetic field is basically zero, and basically,no torque is generated for the motor, which helps greatly reduce stressof a drive system.

The direct current charging method of the power battery and thecorresponding system and apparatus according to the present disclosuremay be applied to but not limited to the foregoing embodiments, and maybe applied to both a full electric vehicle, a plug-in hybrid vehicle,and other vehicle types.

Further, another embodiment of the present disclosure provides avehicle, and the vehicle includes the motor control circuit provided inthe foregoing embodiments.

The foregoing embodiments are merely intended for describing thetechnical solutions of the present disclosure, but not for limiting thepresent disclosure. Although this application is described in detailwith reference to the foregoing embodiments, persons of ordinary skillin the art should understand that they may still make modifications tothe technical solutions described in the foregoing embodiments or makeequivalent replacements to some technical features thereof, withoutdeparting from the spirit and scope of the technical solutions of theembodiments of the present disclosure, which being included in theprotection scope of the present disclosure.

1. A motor control circuit, comprising: a first switch module, athree-phase inverter, and a control module, wherein: a power supplymodule, the first switch module, the three-phase inverter, and athree-phase alternating current motor form a current loop, midpoints ofthree phase legs of the three-phase inverter are respectively connectedto three phase coils of the three-phase alternating current motor, thethree-phase alternating current motor inputs or outputs a current byusing a wire N extending from a connection point of the three phasecoils, the control module is separately connected to the three-phaseinverter, the first switch module, the three-phase alternating currentmotor, and the power supply module, and the control module controls thethree-phase inverter, so that the motor control circuit receives avoltage of the power supply module and outputs a direct current.
 2. Themotor control circuit according to claim 1, wherein: the motor controlcircuit further comprises a second switch module, the three-phaseinverter is connected to a power battery by the second switch module,and the second switch module is connected to the control module.
 3. Themotor control circuit according to claim 2, wherein: a first terminaland a second terminal of the first switch module are connected to apositive electrode and a negative electrode of the power supply module,a third terminal of the first switch module is connected to theconnection point of the three phase coils in the three-phase alternatingcurrent motor, a fourth terminal of the first switch module is connectedto a second terminal of the three-phase inverter and a second terminalof the second switch module, a first terminal of the three-phaseinverter is connected to a first terminal of the second switch module,and a third terminal and a fourth terminal of the second switch moduleare connected to a positive electrode and a negative electrode of thepower battery.
 4. The motor control circuit according to claim 2,wherein: the first switch module comprises a first switch and a secondswitch, the second switch module comprises a third switch and a fourthswitch, a first terminal and a second terminal of the first switch arerespectively the first terminal and the third terminal of the firstswitch module, a first terminal and a second terminal of the secondswitch are respectively the second terminal and the fourth terminal ofthe first switch module, a first terminal and a second terminal of thethird switch are respectively the first terminal and the third terminalof the second switch module, and a first terminal and a second terminalof the fourth switch are respectively the second terminal and the fourthterminal of the second switch module.
 5. The motor control circuitaccording to claim 1, wherein: the first switch module is the firstswitch, and the first switch is connected between the positive electrodeof the power supply module and the connection point of the three phasecoils of the three-phase alternating current motor; or the first switchmodule is the second switch, and the second switch is connected betweenthe negative electrode of the power supply module and the secondterminal of the three-phase inverter.
 6. The motor control circuitaccording to claim 2, wherein: the second switch module is the thirdswitch, and the third switch is connected between the first terminal ofthe three-phase inverter and the positive electrode of the powerbattery; or the second switch module is the fourth switch, and thefourth switch is connected between the second terminal of thethree-phase inverter and the negative electrode of the power battery. 7.A power battery charging method for a motor control circuit including afirst switch module, a three-phase inverter, and a control module,wherein a power supply module, the first switch module, the three-phaseinverter, and a three-phase alternating current motor form a currentloop, midpoints of three phase legs of the three-phase inverter arerespectively connected to three phase coils of the three-phasealternating current motor, the three-phase alternating current motorinputs or outputs a current by using a wire N extending from aconnection point of the three phase coils, the control module isseparately connected to the three-phase inverter, the first switchmodule, the three-phase alternating current motor, and the power supplymodule, and the control module controls the three-phase inverter, sothat the motor control circuit receives a voltage of the power supplymodule and outputs a direct current, wherein the charging methodcomprises: obtaining a voltage of the power supply module and a voltageof a power battery, and selecting a charging manner based on the voltageof the power supply module and the voltage of the power battery, whereinthe charging manner comprises a boost charging manner and a directcharging manner; and controlling the first switch module to close sothat the power supply module outputs a direct current, and controllingthe three-phase inverter so that the power supply module charges thepower battery in the selected charging manner.
 8. The power batterycharging method according to claim 7, wherein the selecting a chargingmanner based on the voltage of the power supply module and the voltageof the power battery comprises: selecting the boost charging manner whenit is detected that a highest output voltage of the power supply moduleis not higher than the voltage of the power battery, wherein thecontrolling the three-phase inverter so that the power supply modulecharges the power battery in the selected charging manner comprises:controlling the three-phase inverter so that a process of charging thethree phase coils of the three-phase alternating current motor by thepower supply module and a process of discharging the power battery bythe power supply module and the three phase coils of the three-phasealternating current motor are alternately performed, to boost a chargingvoltage of the power supply module before the power battery is charged.9. The power battery charging method according to claim 8, wherein thepower supply module, the first switch module, the three-phasealternating current motor, and the three-phase inverter form a chargingloop, and the power supply module, the first switch module, thethree-phase alternating current motor, the three-phase inverter, and thepower battery form a discharging loop; and the controlling thethree-phase inverter so that a process of charging the three phase coilsof the three-phase alternating current motor by the power supply moduleand a process of discharging the power battery by the power supplymodule and the three phase coils of the three-phase alternating currentmotor are alternately performed comprises: controlling the three-phaseinverter to perform alternate closing on the charging loop and thedischarging loop.
 10. The power battery charging method according toclaim 8, wherein: the three-phase inverter comprises three phase legs,each phase leg comprises two power switch units connected in series, andthe three phase coils of the three-phase alternating current motor areseparately connected to connection points of the two power switch unitsof the phase leg; and the controlling the three-phase inverter so that aprocess of charging the three phase coils of the three-phase alternatingcurrent motor by the power supply module and a process of dischargingthe power battery by the power supply module and the three phase coilsof the three-phase alternating current motor are alternately performedcomprises: controlling two power switch units on at least one phase legof the three-phase inverter to close alternately so that the process ofcharging the three phase coils of the three-phase alternating currentmotor by the power supply module and the process of discharging thepower battery by the power supply module and the three phase coils ofthe three-phase alternating current motor are alternately performed. 11.The power battery charging method according to claim 10, wherein thecontrolling two power switch units on at least one phase leg of thethree-phase inverter to close alternately comprises: obtaining aquantity of to-be-connected phase legs of the three-phase inverter basedon to-be-charged power of the power battery, and based on the quantityof to-be-connected phase legs, controlling a corresponding quantity ofphase legs to operate.
 12. The power battery charging method accordingto claim 11, wherein the obtaining a quantity of to-be-connected phaselegs of the three-phase inverter based on to-be-charged power of thepower battery, and based on the quantity of to-be-connected phase legs,controlling a corresponding quantity of phase legs to operate comprises:determining that the quantity of to-be-connected phase legs of thethree-phase inverter is 1 when the control module detects that theto-be-charged power of the power battery is lower than first presetpower, and controlling any phase leg in the three phase legs to operateor controlling the three phase legs to operate alternately.
 13. Thepower battery charging method according to claim 11, wherein theobtaining a quantity of to-be-connected phase legs of the three-phaseinverter based on to-be-charged power of the power battery, and based onthe quantity of to-be-connected phase legs, controlling a correspondingquantity of phase legs to operate comprises: determining that thequantity of to-be-connected phase legs of the three-phase inverter is 2when the control module detects that the to-be-charged power of thepower battery is not lower than the first preset power but lower thansecond preset power, and controlling any two phase legs in the threephase legs to operate or controlling three groups of two phase legs inthe three phase legs to operate in sequence, wherein the three-phaseinverter comprises an A-phase leg, a B-phase leg, and a C-phase leg, afirst group of two phase legs comprise the A-phase leg and the B-phaseleg, a second group of two phase legs comprise the A-phase leg and theC-phase leg, and a third group of two phase legs comprise the B-phaseleg and the C-phase leg.
 14. The power battery charging method accordingto claim 13, wherein after the determining that the quantity ofto-be-connected phase legs of the three-phase inverter is 2 when thecontrol module detects that the to-be-charged power of the power batteryis not lower than the first preset power but lower than second presetpower, the method further comprises: there is a 180-degree differencebetween phases of PWM control signals sent by the control moduleseparately to the two phase legs.
 15. The power battery charging methodaccording to claim 11, wherein the obtaining, by the control module, aquantity of to-be-connected phase legs of the three-phase inverter basedon to-be-charged power of the power battery, and based on the quantityof to-be-connected phase legs, controlling a corresponding quantity ofphase legs to operate comprises: determining that the quantity ofto-be-connected phase legs of the three-phase inverter is 3 when thecontrol module detects that the to-be-charged power of the power batteryis not lower than the second preset power, and controlling the threephase legs to operate simultaneously.
 16. The power battery chargingmethod according to claim 15, wherein after the determining that thequantity of to-be-connected phase legs of the three-phase inverter is 3when the control module detects that the to-be-charged power of thepower battery is not lower than the second preset power, the methodfurther comprises: sending PWM control signals at the same phase to thethree phase legs; or sending PWM control signals at different phases tothe three phase legs, wherein differences between a phase of a PWMcontrol signal of one phase leg and phases of PWM control signals of theother two phase legs are 120 degrees and −120 degrees respectively. 17.A vehicle, comprising: a motor control circuit, wherein the motorcontrol circuit comprises: a first switch module, a three-phaseinverter, and a control module, wherein: a power supply module, thefirst switch module, the three-phase inverter, and a three-phasealternating current motor form a current loop, midpoints of three phaselegs of the three-phase inverter are respectively connected to threephase coils of the three-phase alternating current motor, thethree-phase alternating current motor inputs or outputs a current byusing a wire N extending from a connection point of the three phasecoils, the control module is separately connected to the three-phaseinverter, the first switch module, the three-phase alternating currentmotor, and the power supply module, and the control module controls thethree-phase inverter, so that the motor control circuit receives avoltage of the power supply module and outputs a direct current.
 18. Thevehicle according to claim 17, wherein: the motor control circuitfurther comprises a second switch module, the three-phase inverter isconnected to a power battery by the second switch module, and the secondswitch module is connected to the control module.